Floating balanced doctor blade or vane



Jan. 24, 1961 G. A. e. FAZEKAS FLOATING BALANCED DOCTOR BLADE 0R VANE- ATTORNEYS Filed Sept. 26, 1956 United States Patent FLOATING BALANCED DOCTOR BLADE 0R VANE Gabriel A. G. Fazekas, Roslyn Heights, N.Y., assignor to The Farmingdale Corporation, Farmingdale, N.Y., a corporation of New York Filed Sept. 26, 1956, Ser. No. 612,308

8 Claims. (Cl. 103-84) This invention relates to a floating balanced doctor blade or vane and more specifically to such a blade designed for use in a fluid pump or the like operating on the viscosity principle, as exemplified by the pumps shown in Modrovsky and Sherwood application Ser. No. 465,078, filed Oct. 27, 1954, now Patent No. 2,777,394, and in Fazekas and Modrey application, Ser. No. 563,750, filed Feb. 6, 1956, of which latter application this is a continuation-in-part.

It is an object of the invention to provide such a blade which will form a sufliciently positive stop for the fluid entrained by relative motion of a rotor and a stator separated by a small clearance space, while ensuring that the blade will retain an adequate measure of mobility in order to be self-adjusting to rapidly or slowly changing conditions. That is, the blade should close, to a considerable extent, the clearance space but must be free to float in a hydraulically balanced state, and not be rigidly fixed in position or subject to binding or jamming under any possible operating conditions.

In the present case, the desired result is attained by the provision of a floating balanced blade designed to operate in a slot which is combined with the pressure fluid discharge port and constitutes a portion thereof. This not only eliminates the danger of the blades sticking or jamming in a fixed and incorrect position with respect to its slot and to the parts providing the clearance space, but also minimizes the space lost as compared to arrangements in which the supply and delivery ports both connect directly with the clearance space. 5

Practical embodiments of the invention are shown in the accompanying drawings, wherein:

Fig. 1 represents a transverse sectional view of a floating balanced blade, mounted in a slot in a stator and designed to close adequately the clearance space between the stator and a rotor;

Figs. 1a and 1b represent detail modifications of the blade, in respect of the cross-sectional shape of the bottom part thereof;

Fig. 2 represents a transverse sectional view of a modified blade arrangement, including a spring;

Fig. 3 represents an elevation view of the blade and spring, partly in section on the line III-III of Fig. 2;

Fig. 4 represents a view, similar to Fig. 1, but showing an alternative arrangement of the delivery port, and

Fig. 5 represents a detail elevation of a portion of the spacing plate 3 as viewed from the right of Fig. 1 or Fig. 2, for instance.

Referring to the drawings, and particularly Fig. 1 there of, a rotor R is assumed to be moving in the direction of the arrow, with respect to a stationary casing or stator C, C" (corresponding to the casing halves 1 and 2 in said application Ser. No. 563,750) with a clearance K between the adjacent surfaces of said rotor and stator, all as more fully explained in the copending applications cited above. A fluid of some viscosity (e.g., an oil to be pumped) is supplied to the clearance at a point downstream from a wiper or doctor blade I (constituting a fluid arresting means) and is drawn from said clearance, for delivery 2,969,020 Patented Jan. 24, 1961 wherever desired, through the port P. The terms downstream and upstream wherever used herein designate directions or locations considered with reference to the direction of movement of the rotor relative to the station'- ary casing, as indicated by the arrow on the rotor. The blade 1 is shown as being generally rectangular in crosssectional form and as being freely mounted with a close sliding fit in the slot 2 formed, for instance, in the casing half C. The casing halves C, C" are shown as being spaced apart by a plate 3 corresponding, to this extent, to the inlet spacer bar 4 of said application Ser. No. 563,- 750; the plate 3 is cut away along its downstream edge to form a plurality of inlet channels 3' communicating laterally with an elongated supply passage 8 in the casing 'C" and downwardly with the clearance space. llt will be noted that the fluid is thus admitted to the clearance space in a zone as near as possible to the doctor blade, so as to be subjected most efliciently to the entrainment effect.

The plate 3 forms the downstream wall of the slot 2 and may be made of relatively wear-resistant material so as to maintain constant the cross-sectional shape of the slot. Said slot has a vertical depth somewhat greater than the corresponding dimension of the blade so that there is an appreciable clearance between the top of the blade and the inner (top) wall 2' of the slot. The delivery port P communicates with the slot, preferably through said wall2 as shown.

The blade may be of extended length, as indicated in Fig. 3, and the slot is of corresponding length. The bottom'surface of the blade is shown in Fig. 1 as being divided by the longitudinal groove 4 (which may be semicircular in cross-section, as shown, or may have any other convenient form) into separate narrow lands 5' and 5", the land 5" along the downstream edge of the blade being capable of resting on the surface of the rotor, while the land 5' along the upstream edge of the blade must always remain out of contact with the rotor surface. That is, the clearance between 5" :and the rotor surface is at all times less than the clearance between 5 and said surface. Possible alternative profiles are illustrated in Fig. la, where the bottom surface 13 of the blade is stepped, and in Fig. 1b where the bottom surface 14 is beveled, there being in each case a narrow land 15 or 15', respectively, along the downstream edge corresponding to the land 5" of Fig. l. The form shown in Fig. 1b will be recognized as corresponding to that appearing at 5 in Fig. 2 of application Ser. No. 563,750.

The upstream side surface of the blade is provided with an elongated recess 6, leaving upper and lower horizontal lands 7' and 7", respectively, through which are formed vertically disposed grooves 8', 8". The downstream side wall of the blade is also provided with an elongated recess 9, between upper and lower horizontal lands 10, 10", respectively. A plurality of small holes 11 connect the recess 6 and the recess 9.

It will be appreciated that, in the operation of a pump, for instance, embodying the structure just described, the fluid entrained by the rotor will form a wedge at an elevated pressure beneath the blade (having a lifting effect thereon) and will flow upward through the grooves 8', 8" to the outlet port P, while creating in the upper part of the slot a force acting downwardly on the top of the blade to counteract the lifting force of the wedge thereunder. At the same time part of the fluid will pass through the holes 11 and create a cushion of pressure on the downstream side of the blade (recess 9 and lands 10', 10") which balances horizontally the pressure on the upstream side (recess 6 and lands 7, 7").

Upon initially putting in operation a pump having such a blade and output port arrangement as described above, there is no hydraulic force acting on the top of the blade to match the lifting force of the wedge under the bladef'theblade may thus be" lifted to" adegree such as to make it quite ineffective or at least to delay its reaching the point of effective operation, which depends o'n'limitirig the; pressure drop" between theiupstreambottom'corner ofthe'lblade andthe entrance ofthefoutlet portto a-valueensurir'ig the application'of aiforce' to the top' of the bladeat least equal to the lifting force of the wedge. "Such a condition is possible because,.for instance, the'pressure on'the'la'n'cl is less than the maximum due to leakage'of thef'fluidpast said land: to a zone of zero (inlet). pressure; thus the average. pressure onithe bottom "of theblade maybe less than the average; (and'substantially uniform) p'ressure'on the top.

The starting problem can be overcomelby'proyiding a spring 12'(Figs.f2. and 3 )"disposed between the'top of the blade and the upper wall 2 of the slot in order to'bias ithe blade toward the rotor. .Such' a spring, which may .be in the form of a leaf of clock-spring material, need. not

exert anygreat amount of'force (compared to the pressures of several thousand p.s'.i. which pumps of this "type can-deliver) so long as 'itis suflicient toprevent any serious degree of lifting of the blade at the beginning of operation and to maintain the total downward force on .the topof the blade (hydraulic plus spring)at a value in excess of the lifting force beneath it, under allcontemplated conditions ofoperation. I

The spring 12 may be-undulated (Fig.3) or provided with appropriately .placed longitudinal slots,.or both, in

order to eliminate the possibility of its blocking materially the entrance to the delivery port P, whenthe latter'is in the position shown in Figs. 1 to 3. 1

While the-outlet port P .is shown as opening through the top wall 2 of the slot, it could, if desired, open through the side wall of the slot'ontheupstream side, -e.g., opposite the recess 6,.the top wallbeing thensolid mounted in any. position whatever withrespect to the earths surface.upside down, sideways, .on end, etc. As an orderof magnitude, the blades presently contemplated are conceived as having a heightof about one inch or less, a length of a few inches, and being adapted for use in connection with a viscous fluid such as oil in a clearance space measured in thousandths or hundredths of an inch, the clearances and certain other dimensions .being obviously greatly exaggerated in the drawings,

for purposes of illustration only.

It will be understood that various changes may be made in the form, construction and arrangement of the 4 several" parts without departing from" the spirit and" scope of the invention.

What I claim is:

' the 'slot.

1. In a pump or the like having a stator and a rotor separated by a clearanceof substantially uniform radial depth and constant volume and provided with means for supplying'a'viscous fiuid to said clearance'a fluid arresting means and mounting therefor comprising, a slot formed in. said stator. and opening into said clearance, an outlet port communicating with said slotfthrough the inner wall thereof, a doctor blade floating .freely in said slot, said blade having a generally rectangular crosssectional'form and' being-provided with-grooves so disposed as to permit the passage of fluid past the blade on its upstream side from the clearance to the outlet port, the blade being further provided on its side faces with longitudinally extending recesses boundedadjacent' "the'topand bottomof the" blade. by relatively narrow flat lands, and the grooves extending across the lands on the upstream .side face of the blade.

2. "AZ fluid arresting 'means and "mounting therefor according to claim 1 in which the blade is provided with at least onepassageconne'cting' the recess on the upstream side face with .the recess on theidownstream side face.

- as to bias the blade toward-the rotor.

4. Afluid arresting means and mounting therefor according, to claim3 in which the spring is locatedbetween the top surface of the blade and the inner wall of 15..A fluid arresting means and mounting therefor according to claim l in which the surface of the blade facing the rotor comprises .a-zone adjacent the downstream edge'of the blade which lies closer to the surface of the rotor than does any other part of said blade surface.

.,6..A.'fluid arresting means. and mounting therefor. according to claim. 5. in which the. surface ofzthe blade facing. the rotor. is longitudinally grooved.

7. A fluid arresting means. andrnountingtherefor according to claim. 5 inwhichthe surface of the bladefacing therotor is stepped.

8. A fluidarresting means and mounting therefor according to claim 5 in which the surfaceof thev blade facing the rotor is at least partially beveled.

ReEerences'Cited in the file of this patent UNITED STATES PATENTS 1,785,444 Groesbeck Dec. 16,' 1930 2,583,633 Cronin Ian. 29, 1952 2,873,683 Sherwood Feb. 17,- 1959 FOREIGN PATENTS 143,556 *Austria Nov.='2 5,- 1935 146,648 Australia -May 29', 1952 

